1. Field of the Invention
The present invention generally relates to a semiconductor device and a method of producing the semiconductor device and, more particularly, to a semiconductor device having leads as outer connecting terminals and a method of producing such a semiconductor device.
2. Description of the Related Art
In recent years, electronic equipment, such as portable telephones and portable personal computers, have been rapidly becoming smaller and thinner. Semiconductor devices mounted in these electronic equipment are now expected to be smaller and thinner accordingly.
FIGS. 1A to 3C illustrate conventional semiconductor devices.
The semiconductor device 1A shown in FIGS. 1A to 2 is of a surface mount package type, and has a package structure called SOP (Small Outline Package). The semiconductor device 1A comprises a semiconductor chip 2, a resin package 3, and leads 4.
The semiconductor chip 2 is mounted on a stage 7, and sealed in the resin package 3. The leads 4 are made up of inner leads 5 electrically connected to the semiconductor chip 2 by wires 8 and sealed in the resin package 3, and outer leads 6A extending outward from the resin package 3. The outer leads 6A are shaped like gull wings so as to be suitable for a surface mount package.
To maintain a desired balance in the semiconductor device 1A, the semiconductor chip 2 is preferably situated in the center of the resin package 3. The stage 7 is situated in a lower position than the inner leads 5 by a length HO shown in FIG. 2, so that the semiconductor chip 2 is situated in the center of the resin package 3.
A semiconductor device 1B shown in FIGS. 3A to 3C has a package structure called SOJ (Small Outline J-lead Package). Like the semiconductor device 1A, the semiconductor device 1B is of the surface mount package type. As the inner structure of the semiconductor device 1B is almost the same as the structure shown in FIG. 2, it is not shown in the drawings. In the SOJ-type semiconductor device 1B, outer leads 6B are bent inward and molded into J-shapes.
However, the SOP-type semiconductor device 1A shown in FIGS. 1A to 1C has the following problem. Since the outer leads 6A extend outward from the resin package 3, the total width W2 of the semiconductor device 1A is far greater than the width W1 of the resin package 3. As a result, the SOP-type semiconductor device 1A is large due to the additional length of the outer leads 6A, and fails to respond to the demand for smaller semiconductor devices.
As for the inner structure of the semiconductor device 1A, the stage 7 is situated in a lower position than the inner leads 5 by the length HO so as to maintain the desired balance in the device. However, with the positional difference between the stage 7 and the inner leads 5, the height H1 of the semiconductor device 1A becomes too high due to the length H0. As a result the semiconductor device 1A fails to satisfy the demand for smaller semiconductor devices.
Also, extending outward from the resin package 3, the outer leads 6A tend to be deformed by an external force, thereby reducing the reliability of the semiconductor device 1A. Particularly, the outer leads 6A formed at the four corners are liable to be deformed.
In the SOJ-type semiconductor device 1B shown in FIGS. 3A to 3C, the outer leads 6B are bent inward and molded into J-shapes, so that the total width W3 of the semiconductor device 1B is smaller than the width W2 of the SOP-type semiconductor device 1A.
However, the length of the J-shaped outer leads 6B protruding from the bottom surface of the resin package 3 is large, thereby increasing the height H2 of the semiconductor device 1B. The SOJ-type semiconductor device 1B can be smaller in a plan view, but cannot be thinner as desired. Also, excellent molding precision is difficult to obtain in the SOJ-type semiconductor device 1B, because the outer leads 6B are greatly bent inward and molded into J-shapes.